A car of mass m moves in a horizontal circular path of radius r meter. At an instant its speed is `Vm//s` and is increasing at a rate of a `m//sec^(2)`. Then the acceleration of the car is:
A. `(a^(2)+(v^(2))/(r))`
B. `sqrt(a^(2)+((v^(2))/(r)))`
C. `a^(2)+((v^(2))/(r))^(2)`
D. `sqrt((a^(2))+((v^(2))/(r))^(2))`